Actinomyces viscosus has been implicated as a potential causative agent in a number of oral diseases. Studies to date have examined factors that influence adherence of the organism, primarily by examining the coaggregation of A. viscosus with streptococcal strains. In this regard, it has been shown that surface antigens localized to A. viscosus fimbriae are required for coaggregation to occur. One of the antigens has been characterized as a cell-associated, lactose-inhibitable lectin, and a number of mutant strains are available lacking this activity. Additional analysis of the factors responsible for biosynthesis and assembly of surface components, however, are hindered by the lack of a genetic system with which to dissect these processes. Thus, the purpose of this investigation is to design appropriate methodologies to facilitate genetic analysis of A. viscosus, strain T14V. THis issue will be approached by the utilization of recombinant DNA techniques and by drawing on information concerning streptomyces genetic systems.